The above statement is one of the central tenets of the relativist ethical theory. Relativism has three fundamental concepts. Firstly, morals are not objective. Secondly, morals can be determined by societies to be whatever they think best. And thirdly, interference in the morals of another society is wrong, since you have no reason to assume that your ethical theories are any better than their's. Relativism is a subjectivist theory of morals, as opposed to an objectivist theory. An objectivist theory attempts to explain how morals can be determined by logic or some other method, and are universal, that is applicable to all people in all circumstances. Subjectivists, being in opposition to this view, claim that there are no objective rights and wrongs, but that each 'unit' must decide for itself what the good and bad actions are in any given circumstance. Where most subjectivist theories differ is in the size of the unit. The purest subjectivism asserts that each individual should be allowed to make up their own morals, but relativism puts the unit size at a society level. Each society determines the morals that shall operate within it.
Arguments for subjective theories are of two sorts, those that attack objectivist theories, thus leading to the only alternative, subjectivist ones, and those that actually give reasons why a subjectivist theory is more reasonable. The principal anti objectivist argument is the question of what these objective morals are based upon. A common answer is some deity, who tells us what it is right and wrong to do. This 'divine command theory' is usually sidelined because it relies upon the existence of a deity, something that has yet to be conclusively proved. However, even assuming that a deity does exist, and that he has told us what is right and what is wrong, we are still entitled to ask why it is right or wrong. Is it right because he says it is, in which case it is not an objective theory, rather a subjective theory, with only one possible unit, or is there some objective morality that only a deity is capable of divining, in which case the problem still remains of the nature of the existence of this morality. Another possible answer to this question is that right and wrong are some of the principle states of the universe, that they are properties that are inherent in all things from the very start. How this is achieved is not clear, since physicist have yet to discover an 'ethical dimension' in which matter exists and moves from right on the one side, to wrong on the other. A third possible explanation of how objective morals exist is Plato's theory of Forms. He proposes a mental universe in concurrent existence with the physical universe, in which the perfect Forms of all things exist, including all ethical concepts. Thus there exists there the perfect Form of piety, of honour, and of the highest Form, the Good. This concept, and its compatriots, are perhaps the only manner in which an objective moral theory can be explained reasonably well, without recourse to an, as yet unproven, deity. However, in order to access this realm of Forms, it is necessary to provide all creatures that should have access, probably only humans, with a soul, some segment of them that transcends this physical universe. Again, there is still no conclusive argument or evidence for a soul, so the theory of Forms must wait upon such a proof before being reasonable.
Arguments for subjectivism are generally scientifically based. The first argument is that, given the multitude of morals in the world, both now and in the past, it seems unreasonable to suggest that almost all, if not all of these cultures have got morality wrong. If an objective morality exists, how are we to determine it? It would require some special sense, such as Moore's 'non-natural qualities', or some form of moral intuition, and whilst many would argue that we do indeed seem to have an intuition concerning what is right and wrong, subjectivists would claim that this is due to factors such as genetics, social conditioning and current circumstance. Indeed, it is possible for the subjectivist too to reason out their morals, not all attribute some form of intuition with the decisions of correctness. One possible line of argument is that since we have been formed by evolution, and that leads to the survival of the best survivors, it can be argued that morals give societies an advantage in continued existence, or even 'reproduction' of a sort, perhaps by integrating other societies. This could well explain both why morals are so similar, and so different, in many countries. In general, similar sorts of morals have arisen in most places, such as the moral inhibition of killing those members of your own society, but some societies have found themselves in conditions that lead to the need to have a different morality in order to survive, such as the cannibal tribes of Papua New-Guinea, where perhaps the most advantageous means of gaining food is cannibalism, and societal evolution has therefore selected for those tribes who use this food source. Should such an evolutionary theory of ethics be true, it seems to fit into neither the subjectivist or objectivist camp too well. It can be argued that there is some sort of external factor involved in determining morals, since it is not a conscious action or thought on our part to create these morals initially, but it is also true that morals are subjectively true for each society, so it seems that this external factor is not consistent. It seems, therefore, that an evolutionary theory would sit best within the subjectivist camp. Indeed, it could well be argued that it fits in well with all the subjectivist theories, since it could be how they arose, and we are merely choosing within the constraints laid down by out society, which does indeed seem to be the case.
This support for subjectivism seems fairly strong, but we must still look at relativism itself. Whilst this is a subjectivist theory, it has several aspects that are not subjectivist at all. Relativism is in total agreement with subjectivism on the grounds of morals being subjective, and in only slight disagreement about the size of the unit, but within reasonable bounds. Where relativism falls down badly is its third premise, that it is wrong for one society to interfere with another. This is quite clearly a statement of morals, and in total contradiction to the first two premises. If morals are for each society to determine, then there can be no overarching statements such as 'it is wrong to...'. Thus, the best relativism can come up with on that front is that for the society from within which the proposer speaks does not agree with moral interference, and this is, in general, untrue. It seems that relativism in this form is self-contradictory, but I do not see the need to have it in this form, it works well without the need to deny interference. One can simply say, depending on your own morals, that it is right or wrong for you to interfere in another society. I would suggest that most societies today would feel in fact morally obliged to try to change the morals of another society if they did not conform with their own. This answer also partly solves the next problem proposed against relativism, that it condones any actions that any society may take, however horrific that action is to other societies. This would seem to be true if interference was not allowed, but if we alter the theory as suggested, there is no reason for the society to hold back, and even if the theory stands as before, it does not suggest condonement, merely that the society refuses to interfere. It may well just disapprove from the sidelines, but would have to continue with its ethics of non-involvement.
It would seem therefore, in response to the initial statement, that the morals operating in each society have no inherent relevance to those in any other society, but that should any society take it upon itself to change another societies morals, it can be both within its own ideas of rights, and therefore be 'right' in its action, and it then introduces a 'relevance' to the two sets of morals. It therefore is fair to say that any society can introduce its own relevance to another society. This is couched in purely philosophical terms, since of course in the world most societies interact constantly, and this interaction brings the morals of different societies into contact, perhaps into conflict, and thus makes them relevant to each other.
J. Cottingham, Western Philosophy: An Anthology (Oxford: Blackwell Publishers, 1997) J. Mackie, Ethics: Inventing Right and Wrong (St. Ives: Penguin Books, 1977) B. Williams, Morality (Cambridge: Cambridge University Press, 1997)